The present application relates to a semiconductor structure and a method for fabricating the same. More particularly, the present application relates to slurry compositions and methods for planarizing a germanium material for use, for instance, with fabrication of semiconductor structures, such as, p-type MOSFETs (PFET) devices.
As the density of semiconductor integrated circuits increases and the corresponding size of circuit elements decreases, one of the key strategies to increase performance at lower operating voltages is to increase carrier mobility in the channel region. By way of an example, the carrier mobility in the channel region may be enhanced, for instance, by employing non-silicon, high mobility charge carrier materials, such as, for example, germanium or a III-V compound semiconductor materials, in the fabrication of the channel region. For instance, germanium, a group IV semiconductor material which, for instance, has a highest hole mobility is utilized for fabrication of PFET devices.
The fabrication of germanium on a semiconductor substrate, such as, a silicon wafer, disadvantageously, leads to several issues such as, for instance, defect densities, owing to lattice mismatch of germanium and the silicon wafer. Aspect ratio trapping is one way to overcome the lattice mismatch which, for instance, includes trapping threading dislocations of the germanium material along the sidewalls of a dielectric layer disposed over the semiconductor substrate, such as, for instance, a silicon substrate. This results in a germanium material that has a lower region containing a first defect density and an upper region of a second defect density that is less than first defect density present in an aspect ratio trench. This upper region of the germanium material extends above the dielectric layer, and is subsequently planarized using one or more chemical mechanical planarization (CMP) processes. Prior art CMP processes tend to cause unwanted damage to the upper region of the germanium material.
Enhancements in CMP processing techniques and slurry compositions employed in such technology is continue to be desired for enhanced performance, while minimizing surface and sub-surface damage of the upper region of the germanium material.